Tank devices, in particular, for SCR tanks of motor vehicles, are known per se. They can comprise, apart from the motor vehicle tank itself, a filling device, having a filler pipe and a filler pipe head for filling the motor vehicle tank via a nozzle, as well as also a ventilation device which has a ventilation outlet for the discharge of gasses into the surroundings of the vehicle.
Precisely in the case of SCR tanks, such as, in particular, urea tanks which are used for exhaust gas after-treatment, the formation of a suitable ventilation device is difficult. Filling of such tanks may be carried out on one hand via nozzles with high filling speeds of up to 40 L/min, on the other hand also via simple canisters or containers, such as, for example, Kruse bottles. This variety of filling requires in terms of the tank device flexible ventilation devices which also enables filling in a short time as well as reliable ventilation.
Moreover, the properties of the intended tank contents, typically aqueous urea solution which tends to form crystals during redrying, must also be taken into account. The use of float valves in ventilation devices is known per se. Such float valves can form an adequate ventilation path at different filling speeds and prevent the escape of fluid through the ventilation outlet. However, as a result of drying out of residues of the tank contents at the movable float with the associated crystal formation, leaks can arise at the float valve.